Simplify the toolchain

[vicary]

Recent renovate PRs have breaking tests, which is ultimately caused by the gradual transitioning towards ESM from upstream dependencies.

When fixing these errors, I found the current toolchain a bit cumbersome and requires more maintenance than I am comfortable with.

The main goal of this issue is to replace existing tools with as many zero-conf services as possible, and prefer more actively maintained dependencies when multiple options are present.

1. renovatebot -> dependabot
2. changesets -> semantic-release
   Preventing me from forgetting to add changesets from time to time, commit messages does everything.
3. size-limit -> andresz1/size-limit-action
4. jest et al. -> vitest
   jest needs humongous amount of configurations to deal with a hybrid of CJS and ESM of deps. Also partial transformIgnorePatterns are really slow, bringing 2-3s tests to 10s locally and >30s on CI.
5. bob-tsm et al. -> vite
   Vite does a good job in hiding a lot of complexities that we don't need to know.
6. graphql-ez et al. -> graphql-yoga + @graphql-tools/mock
   A more actively maintained alternative.
7. Simplify file structure
   1. Remove scripts/* and transition to an ESM-first codebase
   2. Remove internal/*
      1. Move internal/images to assets/
      2. internal/test-utils should be superseded by vitest which we should try to make do with only the defaults.